AC electro-osmosis micro-fluidic device for pumping and mixing liquids and method for pumping and mixing liquids

ABSTRACT

Disclosed herein is a device for mixing micro-fluids while pumping them or a device for pumping and simultaneously mixing the liquids and bio-molecules and a method for mixing and simultaneously pumping the liquids, and more particularly to a device for mixing and pumping micro-fluids having electrode pairs, in which each pair consists of two electrodes: an electrode pair having a first electrode and a second electrode with a greater width than the first electrode are disposed in parallel, provided on at least one internal face of a liquid channel and a method for mixing and pumping micro-fluids by applying an alternating current voltage to the electrode pair. 
     According to the present invention, an alternating current electro-osmosis occurs near an electrode pair comprising a relatively narrow electrode and a wide electrode to produce complicate flow characteristics so that liquids are effectively mixed and simultaneously pumped in the fields of a small medical device or a small fluid device, etc.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, generally, to alternating currentelectro-osmosis micro-fluidic devices for mixing and pumping liquids andmethods thereof, more particularly, to a device for mixing and pumpingmicro-fluids having electrode pairs, in which each pair consists of twoelectrodes: an electrode pair having a first electrode and a secondelectrode with a greater width than the first electrode are disposed inparallel, provided on at least one internal face of a liquid channel anda method for mixing and pumping micro-fluids by applying an alternatingcurrent voltage to the electrode pair.

2. Description of the Related Art

One of the important problems in a lab-on-a-chip field which is a smallmedical device for diagnosing and curing a disease is to mix and pumpmicro-fluids.

In general, an infinitesimal amount of reagents comprising thesemicro-fluids or these reagents mixed with bio-molecules such as DNA, RNAor erythrocyte should be moved to the next step to be diagnosed.

Lap-on-a-chips include a lot of fluid channels in order to mix andtransfer micro-fluids and bio-molecules. However, as the fluid channelused in the lab-on-a-chip has a very small cross-section less thanhundreds μm, it is not easy to mix or pump the fluids with a relativelylarge viscosity.

Accordingly, attempts to invent various methods to mix the fluids in themicro-fluid channels have been made.

The representative one of the conventional methods is to mix a fluid orfluids with bio-molecules in a channel by changing the shape of thechannel disclosed by Strook et., al. (A. D. Strook, S. K. W. Dertinger,A. Ajdari I. Mezic, H. A. Stone, G. M. Whitesides, “Chaotic mixer formicro-channels”, Science, Vol. 295, pp. 647, 2002.)

In other words, it is a technology to make a herringbone-shaped grooveat the bottom of the micro-fluid channel and mix the fluids.

However, these methods have a disadvantage to make complicated channels.

In the meantime, various methods for pumping a small amount ofmicro-fluids have been researched and the researches on a small pumphave mainly been carried out. This is a method for pumping a liquid byapplying a pressure on the fluid mainly using mechanical methods.

However, this method requires for an individual machine for applying apressure to a fluid and causes a problem that the small fluidic deviceor the lab-on-a-chip becomes more complicated and is difficult to beminiaturized.

Another method for pumping a liquid is an electric method, using anelectro-osmosis phenomenon.

The method using this electro-osmosis is classified into a method forapplying a direct current and a method for applying an alternatingcurrent.

The method for pumping micro-fluids by the electro-osmosis applying adirect current requires a voltage of several kV to be applied. This highvoltage makes it difficult to customize a small fluidic device and hasfatal disadvantages in changing characteristics of object fluids andbio-molecules as well as affecting the stability of a machine.

On the contrary, according to the electro-osmosis method for applying analternating current, micro-fluids are moved just by applying a voltageof several V (A. B. D. Brown, C. G. Smith and A. R. Rennie, “Pumping ofwater with ac electric fields applied to asymmetric pairs ofmicroelectrodes,” Physical Review E, Vol. 63, 016305, 2002).

As described above, researches in the fields of mixing a small amount ofmicro-fluids and pumping the micro-fluids have been individually carriedout. Accordingly, a fluid mixer and a pump exist separately in alab-on-a-chip field including a small micro-fluidic device so far.

SUMMARY OF THE INVENTION

An object of the present invention is to provide with a device formixing and pumping complicate micro-fluids, which is capable of pumpingand simultaneously mixing a small amount of micro-fluids or mixingfluids with bio-molecules (DNA, RNA and erythrocyte, etc.).

In addition, another object of the present invention is to provide witha method for providing with a miniaturized and highly integrated deviceby integrating mixing and pumping liquids and a method for manufacturingsuch device conveniently.

In order to attain the above objects, the micro-fluidic device forpumping and mixig micro-fluids according to the present invention isprovided with electrode pairs, in which each pair consists of twoelectrodes: an electrode pair having a first electrode and a secondelectrode with a greater width than the first electrode on at least oneinternal face of a liquid channel.

The liquid channel may have a tubular shape but can have any shape ofcross-sections of the tube.

The liquid channel may be a micro-fluidic channel.

The liquid channel may be made of an insulating glass or a polymercompound.

The device for mixing and pumping micro-fluids according to the presentinvention may be a device including the liquid channel or a devicecomprising the liquid channel itself.

The electrode pairs may have a linear or a curved strip shape and atleast one electrode pair has a bend or more.

The electrode pair according to the present invention is characterizedby that a voltage is applied by an alternating current power source.

According to the present invention, the cross-section of the liquidchannel is not confined to a rectangular shape, i.e., the shape can be acircle, triangle, pentagon and hexagon, etc., and the entire liquidchannel may have either a linear or a curved shape.

The cross-section of the liquid channel is within hundreds μm.

According to the present invention, the components of the electrode maybe a conducting metal, especially gold, silver, titanium, platinum,copper or their mixtures. The components of the electrode are notlimited by the said metal and may be whichever is an electricallyconducting material used in the electro-osmosis method in the level ofthose skilled in the present invention.

It is preferable that the widths of the electrodes be within tens μm andmore preferable that the first electrode and the second electrode befrom 1 to 90 μm, but the width of the first electrode is required to bea relatively small in comparison with that of the second electrode.

According to the present invention, at least one electrode pair isprovided in a length direction or a width direction of the liquidchannel.

In order to obtain the above objects, a method for mixing and pumpingliquids according to the present invention comprises: providing withelectrode pairs, in which each pair consists of two electrodes: anelectrode pair having a first electrode and a second electrode with agreater width than the first electrode on at least one internal face ofa liquid channel and mixing and pumping liquids by applying a voltagethrough an alternating current power source.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a cross-sectional view seeing through the inside of a devicefor mixing and pumping liquids in accordance with an embodiment of thepresent invention;

FIG. 2 is a cross-sectional view of a device for mixing and pumpingliquids in accordance with an embodiment of the present invention by thecross-section 1 of FIG. 1;

FIG. 3 is an upper face view schematizing the main flow direction of afluid in a device for mixing and pumping liquids including at least twoelectrode pairs in accordance with an embodiment of the presentinvention;

FIG. 4 is an upper face view of an electrode pair for mixing and pumpingliquids in accordance with an embodiment of the present invention;

FIG. 5 is an upper face view of a device for mixing and pumping liquidshaving at least two electrode pairs and of which the liquid channel iscurved; and

FIGS. 6 and 7 are upper face views of the shapes and patterns ofelectrode pairs for mixing and pumping liquids with the electrode pairaccording to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the attached drawings. Reference now should bemade to the drawings, in which the same reference numerals are usedthroughout the different drawings to designate the same or similarcomponents in the following description of the present invention.

In addition, detailed descriptions may be omitted if it is determinedthat the detailed descriptions of related well-known functions andconstructions may make the gist of the invention unclear.

According to an embodiment of the present invention, asymmetricelectrode pairs are provided in a liquid channel, especially on aninternal face of a fluid channel in order to mix the micro-fluids in aherringbone or a diagonal shape. In other words, the electrodes areprovided to have a bent shape while forming regular angles in theproceeding direction of a fluid channel in disposing the electrodes.

In FIG. 1, which is a cross-sectional view seeing through the inside ofthe device for mixing and pumping micro-fluids according to anembodiment of the present invention, a micro-fluid channel (100) with aplurality of electrode pairs (103) disposed on one face is suggested,each having a first electrode (101) and a second electrode (102).

At least one electrode pair may be disposed regularly or irregularlywith a periodic instance, and may be disposed on at least one faceinside the micro-fluid channel (100).

When disposing several electrode pairs, the electrode pairs may havebeen disposed in different types, and the distance between a firstelectrode and a second electrode in one electrode pair may differ fromone electrode pair to another electrode pair.

FIG. 2 shows a cross-section according to the present invention viewedbased on the cross-section 1 of FIG. 1.

Referring to FIG. 2, the upper and the lower portions are the upper andthe lower part of a liquid channel made of an insulating material likeglass, in which a fluid is flown.

According to an embodiment of the present invention, electrodes areprovided at a lower portion of the micro-fluid channel, one electrodepair (203) having a first electrode (201) and a second electrode (202)disposed in parallel.

If the width of the first electrode (201) is W1 and the width of thesecond electrode (202) is W2, W1 is smaller than W2.

The first electrode (201) and the second electrode (202) are disposed inparallel but electrically isolated because of the predetermined interval(G1) therebetween.

In addition, when a plurality of electrode pairs are disposed, theelectrode pairs have the predetermined interval (G2) therebetween sothat electrode pairs can be electrically insulated each other.

Referring to FIG. 2, several electrode pairs are electrically connectedby alternating current power source. In other words, the firstelectrodes of the several electrode pairs are connected with oneterminal of the alternating current power source and the secondelectrodes are connected with the other terminal of the alternatingcurrent power source.

And then, when an alternating current power source is applied, the fluidon the electrode has a polarity electrically and the fluid moves by thereaction of an electric field. The direction of the force exerted onfluid is always the same, since the polarity of fluid over the electrodeand the direction of the electric fields there change simultaneously inaccordance with an alternating current source.

The voltage of the alternating current power is a unit of several volts,in other words, a comparatively low voltage is applied.

The portion where the fluid is supported is the one just on theelectrode and the direction to be supported is shown in FIG. 3.

In other words, as shown in FIG. 3, the fluid moves in the directionfrom the first electrode (301) with a small width to the secondelectrode (302) with a large width, perpendicular to the lengthdirection where the electrode is arranged.

According to the embodiment of the present invention shown in FIG. 3,the arranged shape of the electrode pair (303) has one bend in theinterim as a linear strip, and the fluid is supported in an arrowdirection and can be pumped and simultaneously mixed.

Accordingly, in order to integrate pumping and mixing micro-fluids, itis preferable to include at least one bend in the disposition structureof an electrode pair.

FIGS. 4 to 7 are upper face views of a device for mixing and pumpingmicro-fluids comprising electrode pairs.

FIG. 4 shows that just one electrode pair (403) is exploded, and thewidth of the first electrode (401) is relatively narrow in comparisonwith that of the second electrode (402) and the angle (α) made by thewall surface at one side of a liquid channel and the electrode pair maybe different from the angle (β) made by the wall surface at the otherside of the liquid channel and the electrode pair. The limitingcondition for mixing and pumping the micro-fluids is that α≠0°, α≠90°and α≠180°, and β≠0°, β≠90° and β≠180°.

Furthermore, the distance (p1) from the wall surface on one side of aliquid channel to one bent point of the electrode pair may or may not bethe same as the distance (p2) from the wall surface on the other side ofthe liquid channel to the same bent point of the electrode pair.

In case that more than one electrode pair is provided, an electrode pairof which the width (W1) differs from the width (W2) may be disposed, andthe electrode pair of which the angle (α) differs from the angle (β) canbe disposed. And the electrode pair of which p1 differs from p2 can bedisposed.

In other words, at least one electrode pair having optional values, W1,W2, α, β, p1, p2 can be provided. The said optional values, W1, W2, α,β, p1, p2 of each electrode pairs can be different values.

The electrode pairs may be disposed regularly or irregularly.

The irregular disposition of the electrode pairs may be a source of amore complex and variable force in mixing and pumping the micro-fluids.

When W1 is set to be different from W2, a from P and p1 from p2 in eachelectrode pair, the capability of mixing the fluid can be remarkablyimproved.

The surface where the electrode pairs are disposed is shown in the upperface views of FIGS. 5 to 7 viewed from the upper side in a device formixing and pumping micro-fluids comprising at least two electrode pairs,but is not necessarily limited to these shapes.

It is preferable that the entire shape of the micro-fluid channel bemainly in a straight line but the fluid channel with an internal surfacehaving a curved line is possible as shown in FIG. 5.

In addition, as shown in FIG. 6, various shapes of electrode pairs (603)can exist in the directions of a width and a length of the liquidchannel.

FIG. 7 shows that the electrode pair (703) is disposed in a linear and adiagonal shape, not a shape in which a part of the electrode pair (703)is bent.

In this shape, micro-fluids can be pumped and mixed, but the effect ofpumping and mixing the microfluids may be low in comparison with aliquid channel having a shape with a bend provided on at least oneelectrode pair of a linear or a curved line strip or a shape withvarious dispositions of such electrode pairs, as described above.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

As described above, according to the present invention, a small amountof micro-fluids are pumped and simultaneously mixed and the number ofthe devices for pumping and mixing the fluids required for manufacturinga micro-fluidic system can be reduced, resulting in simplifying theentire system. Also, according to the present invention, the possibilitycausing malfunctions is decreased.

In addition, a lab-on-a-chip capable of carrying out simultaneouslymixing and pumping is provided to have an effect on miniaturizing andhighly integrating a device.

There is an advantage in that there are no difficulties to adopt thisdevice in the existing electronic device or a system by using anelectricity in both pumping and mixing a fluid.

Furthermore, according to the present invention, a driving voltage islow and safe by far in comparison with a micro-fluidic device of theother electro-osmosis method and it consumes extremely little power tobe very useful economically.

1. A micro-fluidic device for pumping and mixing liquids provided withelectrode pairs, in which each pair consists of two electrodes: anelectrode pair having a first electrode and a second electrode with agreater width than the first electrode on at least one internal face ofa liquid channel.
 2. The device of claim 1, wherein the electrode pairshave a linear or a curved strip shape.
 3. The device of claim 2, whereinat least one electrode pair has at least one bend in its shape.
 4. Thedevice of claim 1, wherein the electrode pairs are applied by a voltagethrough an alternating current power source.
 5. The device of claim 1,wherein the cross-section of the liquid channel is one selected from thegroup consisting of substantially a circle, triangle, rectangle,pentagon and hexagon.
 6. The device of claim 1, wherein the liquidchannel has a linear or a curved shape.
 7. The device of claim 1,wherein the electrodes are conducting metals.
 8. The device of claim 1,wherein the widths of the first electrode and the second electrode are 1to 90 μm.
 9. The device of claim 1, wherein at least one electrode pairis provided in a length direction or a width direction of the liquidchannel.
 10. A method for mixing and pumping liquids, which comprises:providing with electrode pairs, in which each pair consists of twoelectrodes: a first electrode and a second electrode with a greaterwidth than the first electrode on at least one internal face of a liquidchannel, mixing and pumping liquids by applying a voltage through analternating current power source.
 11. The method of claim 10, whereinthe electrode pair has a linear or a curved strip shape including atleast one bend.
 12. The method of claim 10, wherein the widths of thefirst electrode and the second electrode are 1 to 90 μm.
 13. The methodof claim 10, wherein at least one electrode pair is provided in a lengthdirection or a width direction of the liquid channel.